In producing, for example, a car, coils are produced in a production unit, the coils are used in a subsequent production unit to produce armatures, the armatures are used in a subsequent production unit to produce motors, the motors are used in a subsequent production unit to produce fuel pumps, the fuel pumps are used in a subsequent production unit to produce fuel pump assemblies, the fuel pump assemblies are used in a subsequent production unit to produce fuel tank assemblies, and the fuel tank assemblies are used in a subsequent production unit to produce cars. A production activity such as parts produced in a former production unit are used in a subsequent production unit to produce high level parts is repeated many times or multi-stages in a normal production chains.
In the present specification, a production unit is numbered from the highest side, and a production unit that produces final product is termed the present production unit. In the example given above, the coils are produced in a sixth production unit, the armatures in a fifth production unit, the motors in a fourth production unit, the fuel pumps in a third production unit, the fuel pump assemblies in a second production unit, and the fuel tank assemblies in a first production unit. The fuel tank assemblies produced in the first production unit are delivered to the present production unit, and the final products (the cars) are produced in the present production unit.
The aforementioned ‘first production unit’ could instead be considered as ‘the present production unit’ in a case that the fuel tank assemblies are produced as final products. In this case, the ‘second production unit’ described earlier is now the ‘first production unit’ and the ‘third production unit’ is now the ‘second production unit’. Any production unit that receives lower parts and produces higher parts by using lower parts can be deemed to be the ‘present production unit’, and the production units preceding it may be termed the ‘first production unit’, ‘second production unit’, ‘third production unit’, etc. The technique of the present invention assists findings of problems by revealing problems existing but concealed within parts supplies chains that supply parts to the present production unit. The technique of the present can be applied to any production unit in which lower level parts are used to produce higher level parts.
To produce high quality final products at a low cost within a short time in a production chains, parts supplies chains for the production chains must be rational. Waste or overburdening should be excluded from the parts supplies chains for the production chains. For example, in each production unit within the parts supplies chains, the rate of defective parts should be low, the number of inventoried parts should be less, production and delivery should take place within a short time, and the number of part suppliers should be reduced to an appropriate number.
However, under present circumstances there is no means for learning whether parts supplies chains are irrational with waste or overburdening, or are rational without waste or overburdening. Japanese Patent Laid Open Publication 2001-331535 and Japanese Patent Laid Open Publication H9-267239 set forth a technique for graphically displaying an overall relation of various parts defined by a product—first level parts list, first level part—second level parts list, second level part—third level parts list and so on. The overall relation defined by the upper level part—lower level parts list at multi-stages is graphically displayed by using linking information defining hierarchic relationship. When a higher level part is designated, it is possible to identify chains of lists of lower level parts at various levels that constitute the higher level part.
Even though the lists of the lower level parts at various levels that constitute the higher level part is shown graphically, it is not possible to know from this graphic display whether the parts supplies chains are irrational with waste or overburdening, or are rational without waste or overburdening.